My Unwrapped Baked texture is mostly bugged
Everything is correct, but before baking you have to make sure you need to create a new image say "untitled.png" in "UV Editor" to bake and add image texture to all the material files that the object have.

In your case you have 2 materials i.e. green one, and yellow one.

Add Image texture with the created image "untitled.png" selected in both the materials and bake diffuse texture with just "color" selected.

Solution gif file --> here (its over 12mb but 2mb limit. so can't upload directly)

Follow the gif file and 

After the baking completes you'll have something like this. Just need to save this to local disk.